Field of the Invention;
The invention relates to a method of making a moisture-binding skin care product on the basis of an oil-in-water emulsion, wherein the water phase and the oil phase are mixed at an elevated temperature and then cooled while stirring and to the products made with this method.
Such a skin care product is known from European Patent 0 258 558 B2. This skin care product consists, in the resting state, of a separate oil-in-water emulsion (o/w emulsion) which is on top of an aqueous phase. This skin care product is especially characterized by the fact that it is free of emulsion stabilizers and that the emulsifying agent is added at a proportion of .ltoreq.1%. A general formulation of this product consists of approx. 10 to 90% lipophilic constituents, approx. 90 to 10% hydrophile constituents and preferably approx. 0.01 to 0.5% emulsifying agent.
Just prior to applying this product to the skin, it is shaken. This results in an unstable oil-in-water emulsion. It was observed at this point that this product corresponds to an o/w emulsion with regard to its spreadability and the individual sensation of the user, while, at the same time, accomplishing the moisture-binding and protective effect of a w/o emulsion. Thus, this skin care product features both the positive characteristics of an o/w emulsion and the favorable characteristics of a w/o emulsion.
As mentioned above, an unstable oil-in-water emulsion is formed after shaking the product. Regarding this point, European Patent 0 258 558 explains further that, after a relatively short period, a phase separation occurs in the forming unstable emulsion in a manner which results in an o/w emulsion with an aqueous phase.
It became evident, however, that the separation into the oil-in-water emulsion and the aqueous phase does not always occur. It became evident, in particular, that, in many cases, a separation into the afore-described phases either did not take place at all or took place only after a very long time (several weeks). A further disadvantage is the fact that the afore-described phases were not stable, i. e., that a further separation of the oil-in-water emulsion took place. A separation into three phases was also observed, i. e., a water phase, the o/w emulsion and an oil layer. For the consumer, however, it is important, also for visual reasons, that the shaking take place starting from an o/w emulsion which is on top of an aqueous phase.
Departing from this basis, it is the object of the present invention to propose a method of making a skin care product according to European Patent 0 258 558, which makes it possible for the resulting skin care product to have a stable o/w emulsion in its resting state on top of an aqueous phase over an extended period of time (at least one year), wherein the formation of the o/w emulsion and the water phase is to take place within a few hours after shaking.